Field of the Invention
This disclosure relates to a sheet storage apparatus and an image forming apparatus including the sheet storage apparatus.
Description of the Related Art
There is a widely used image forming apparatus such as a copier, a printer, and a facsimile, which feeds a sheet stored in a sheet storage apparatus to an image forming portion and forms an image. This kind of sheet storage apparatus includes a plate-shaped sheet stacking member on which sheets are stacked, with the sheet stacking member being vertically movable. The sheet stacking member is lowered upon replenishing the sheets. When feeding the sheets, the sheet stacking member is lifted to move the upper surface of the stacked sheet to a position in which the sheet can be fed by a pickup roller located above the sheet stacking member. In addition, the sheet storage apparatus is mounted on an apparatus body in a drawable manner. When storing the sheet, the sheet storage apparatus is drawn out, and then the sheets are set on the sheet stacking member from above.
A sheet storage apparatus disclosed in JP-A-2010-83645 is provided with a trailing end regulating member regulating the upstream ends in a sheet feeding direction (hereinafter, referred to as the trailing ends) of the sheets, which are stacked on a sheet stacking member. The trailing end regulating member is configured to be movable along the sheet feeding direction so that multiple kinds of sheets with different sizes can be stored. In addition, the sheet storage apparatus is provided with side end regulating members which regulate side ends of the sheets in a direction (hereinafter, referred to as a width direction) orthogonal to the sheet feeding direction of the sheets and are movable in the width direction. Then, the side ends of the sheet are regulated by the side end regulating members while the trailing end of the sheet is regulated by the trailing end regulating member, and thereby the position of the sheet is regulated in a predetermined position.
JP-A-04-333429 discloses a configuration that a trailing end regulating plate provided in a sheet feed deck is movable to a regulating position on which the trailing end regulating plate regulates a sheet trailing end and a retracting position on which the trailing end regulating plate is away from the sheet, in accordance with the sheet size. Then, in a case where sheets of a large size are stored, the trailing end regulating plate is tilted down by substantially 90° from a regulating position so as to release the regulating operation of the trailing end, being stored in a lifter plate. This configuration can be used to store the sheets of a large size in a downsized sheet feeding deck.
However, in such a conventional sheet storage apparatus, a thickness of the trailing end regulating member is required to ensure a certain degree of stiffness so as to fulfill a regulating function for the trailing ends of the sheets. Thus, in a case where the trailing end regulating member movable in the sheet feeding direction is used, a length of the sheet storage apparatus in the sheet feeding direction is required to be at least the sum of a length of the maximum size of the sheets to be stored and a thickness of the trailing end regulating member. That is, the sheet storage apparatus with the trailing end regulating member movable in the sheet feeding direction is tend to be long, which leads to enlargement of the sheet storage apparatus.
It is possible to use a trailing end regulating plate that can be stored in the lifter plate so as to prevent enlargement of the sheet storage apparatus. In this case, however, it is required a holding mechanism to hold the trailing end regulating plate, which has been lifted up, in a right angle accurately, thereby leading to increase in cost. Furthermore, since the trailing end regulating plate is tilted and laid down on the sheet feed deck, a thickness of the trailing end regulating plate may negatively affect a sheet storage height, that is, a stacking amount of the sheets.
Here, when using side end regulating members movable in the width direction, the side end regulating members need to be arranged on a downstream side in the sheet feeding direction so as to regulate the side ends of the sheet of the minimum size, of which a length in the sheet feeding direction is the minimum among the sheets to be stored in the sheet storage apparatus. However, when storing sheets having a greater length in the sheet feeding direction than that of the minimum size, the side end regulating members arranged in such a position might not sufficiently regulate the upstream portion, in the sheet feeding direction, of the side ends of the sheets. Thus, there is a case that the side ends on the trailing end portion of the sheet is not sufficiently regulated, and decrease in the stability of sheet feeding operation might occur.